Marine biofouling is present in all oceans and at all depths. Its character and magnitude are a function of physical and biological factors. Basically, marine growth varies as a function of temperature, food and light intensity. The mechanisms of marine biofouling are known and can be divided into the following five phases: (1) adsorption of organic molecules by the fouling surface (2) attachment of bacteria to the fouling surface, partially facilitated by the absorbed organic molecules (3) growth of bacteria and colony formation (4) accumulation of additional organic material and film formation (microfouling) and finally, (5.) the attachment and growth of larger organisms (macrofouling), by organisms such as barnacles, mussels, etc.
The detrimental effects of marine biofouling are well known and wide ranging. Biofouling affects the performance and efficiency of ships, commercial boating and marine installations, and is a major problem for the marine industry today. The same is also true of commercial coastal facilities, such as water treatment plants, power generation plants, oil platforms, etc.
Therefore, many attempts have been made to control biofouling. Periodic cleaning was probably the first method of control attempted. Copper cladding had been used on earlier wooden ships.
More recently, new techniques such as the use of new toxic paints, and toxic plastic materials have been devised. In addition, toxic chemicals made from seawater, by electrolysis or by introduction into the water, to kill the organisms are also currently in use. However, none of these methods have been entirely effective for controlling biofouling problems.
Tri-butyl tin oxide (TBTO) and copper-base paint systems have been traditionally used on Navy ships as a marine anti-foulant. TBTO is an environmental and health hazard and its use has been restricted. The copper-base paint type systems presently in use still present somewhat of a health hazard. Both the TBTO and the copper-base paint type systems are only effective under limited conditions.
Chlorinator systems are presently in use in Navy ships, commercial ships and marine facilities. However, chlorinator systems are also toxic. These systems are effective for the problem of marine biofouling in intakes and heat exchangers. Nevertheless, fouling of intakes, sea chests, tanks, on optical windows and hydrophones has continued. New methods and systems are needed to reduce the marine fouling in Navy and commercial ships and in commercial facilities, especially for pipes and intakes, cooling towers, transducer surfaces, optical windows and external mechanisms.
Further, most of the prevention systems in use today are toxic to the environment. New programs established by the U.S. government and commercial industries aimed at "zero emissions" into the environment of toxic waste, are being implemented. Eventually a major portion of the currently used biofouling techniques will have to be eliminated to preserve the nation's water resources, especially in the Great Lakes. It has been found that what was originally thought to be safe toxic levels for marine life are in fact not. For example, findings show that the tolerance to organochlorines is much lower in fish than in mice. Preliminary research indicates that fish may be 1000 times more susceptible to organochlorine poisoning than mice. With such recent environmental concerns, greater and greater limitations will be placed on the present biofouling prevention techniques.
Accordingly, an object of this invention is to provide a solution to biofouling which is non-polluting to both the outlying and local environments, and is simplistic and reliable in application to the biofouling problem. It is therefore proposed, in accordance with the present invention, to apply the use of ultraviolet light for the prevention of marine biofouling. The ultraviolet power needed to prevent the biofouling from starting even at phase 2, is minimal, and recent experimental work clearly shows that UV prevention methods work effectively. A method is described herein in which ultraviolet light can be used to control biofouling by preventing attachment of marine organisms, stunning the organisms and also by exterminating the organisms.